1. Field of the Invention
Aspect of the present invention relate to a process cartridge and an image forming apparatus detachably equipped with a process cartridge.
2. Description of the Related Art
An image forming apparatus detachably equipped with a process cartridge has been known. This process cartridge includes a developing unit equipped with at least a developing roller and a developing frame member, and a photosensitive member unit equipped with at least a photosensitive drum and a cleaning frame member. And, the developing roller is brought into contact with a photosensitive drum on which an electrostatic latent image is formed, whereby the electrostatic latent image is developed to form a toner image as a developed image. This system, in which development is performed by bringing a developing roller into contact with a photosensitive member drum, is referred to as a contact developing method.
In this contact developing method, the developing roller is kept pressed against the photosensitive drum so that the developing roller and the photosensitive drum maintain a predetermined abutting pressure. Thus, an elastic layer on the surface of the developing roller undergoes deformation, resulting in a defective image. To cope with this problem, it might be possible, for example, to select a material little subject to deformation for the elastic layer on the surface of the developing roller, or to strictly control the manufacturing conditions. That, however, may involve an increase in cost.
In view of this, Japanese Patent Application Laid-Open No. 2008-170950 discusses a configuration in which the developing roller is kept away from the photosensitive drum by means of a separation member during the non-image-formation period in which no image formation is performed.
Further, also in a configuration as discussed in Japanese Patent Application Laid-Open No. 2010-190977 (see FIG. 11), it is possible to separate a developing roller 17 from a photosensitive drum 1. In the configuration illustrated in FIG. 11, development separation portions 70 (70a and 70b) are provided at two positions in a developing unit 4, i.e., on the upstream side and the downstream side of a process cartridge 7. And, when the process cartridge 7 is attached, the development separation portions 70 (70a and 70b) of the process cartridge 7 are pressed by a guide member 29 provided in the image forming apparatus main body, whereby the developing roller 17 is separated from the photosensitive drum 1.
In the above-described configuration illustrated in FIG. 11, the development separation portions 70 of the process cartridge 7 are engaged with a groove provided in the guide member 29 in a state in which the attachment of the process cartridge 7 to the image forming apparatus has been completed. In a configuration like this, in which there is a difference in height between the guide member 29 and the grove, the operability when attaching the process cartridge 7 may be affected. Further, the guide member 29 provided in the image forming apparatus main body is formed so as to extend from the upstream side to the downstream side in the attachment direction of the process cartridge 7, which means it leaves room for an improvement in terms of space saving inside the image forming apparatus main body.